Birth defects constitute one of the major problems of human and veterinary medicine. This project seeks to develop and exploit viable animal models of viral teratogenesis which may be directly applicable to veterinary medicine and which may provide insight into the pathogenetic mechanisms underlying some human fetal malformations. Congenital hog cholera infections have been extensively studied in this laboratory. Work is continuing at an in vitro level studying cell- virus interactions by virologic, immunofluorescent, audioradiographic, histologic, and ultrastructural techniques. Primary fetal brain cultures are being used for the above studies. Fetal infections with guinea pig cytomegalovirus are being studied to elicit the route of virus from maternal infection through the placenta and into the fetus. Sites of viral replication, type of pathology, and effect of the developing immune system on the infected guinea pig fetus will be analyzed. Pathologic tissues derived from malformed human fetuses are being analyzed by virologic, immunofluorescent, histologic, and ultrastructural techniques in an effort to discover new agents which may have a teratogenic potential in man.